Rituximab, Yttrium Y 90 Ibritumomab Tiuxetan, Melphalan, and Autologous Peripheral Stem Cell Transplant in Treating Patients With Previously Treated Multiple Myeloma

RATIONALE: Monoclonal antibodies, such as rituximab, can block cancer growth in different ways. Some block the ability of cancer cells to grow and spread. Others find cancer cells and help kill them or carry cancer-killing substances to them. Radiolabeled monoclonal antibodies, such as yttrium Y 90 ibritumomab tiuxetan, can find cancer cells and carry cancer-killing substances to them without harming normal cells. Drugs used in chemotherapy, such as melphalan, work in different ways to stop the growth of cancer cells, either by killing the cells or by stopping them from dividing. A peripheral stem cell transplant using stem cells from the patient may be able to replace blood-forming cells that were destroyed by chemotherapy. Giving monoclonal antibody therapy together with chemotherapy and autologous peripheral stem cell transplant may kill more cancer cells. PURPOSE: This phase I trial is studying the side effects and best dose of yttrium Y 90 ibritumomab tiuxetan when given together with rituximab, melphalan, and autologous peripheral stem cell transplant in treating patients with previously treated multiple myeloma.